Optical Coherence Tomography (OCT) is widely accepted as a technique for acquiring tomographic images of a living body (see Non-Patent Document 1). OCT is a technique with significant potential for in vivo provision of morphological information having a spatial resolution of about 1 to 10 μm in a depth direction noninvasively and without exposure to harmful radiation.
In OCT, light reflected or scattered once within a biological sample is detected. The detection is conducted by means of a Michelson interferometer configuration, in which an interference component of light returned from the living body (hereinafter referred to as inspection light) and reference light is used as a signal. If relative delay time, between the inspection light and the reference light is within the coherence time of a light source, a stable interference signal can be obtained. OCT utilizes the stable interference signal.